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Audio Calibration
I’m just setting up my new suite and am having trouble seting up my metering.
I have calibrated PPM’s that are set -18db 4ppm but when my FCP tone is set to -18db the analogue out of the card is over 6ppm. To get 4ppm I have to drop the tone to -23db in FCP. I can’t find anywhere to change the output gain from the card. Am I doing something wrong? Are the FCP values useless? Also my vectorscope is over by quite a bit whilst showing safe in FCP. What am I missing?
BTW 2×2.5 G5, FCPHD, 1.5GB RAM, Decklink Extreme.
Lex
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12 Replies
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I’ve always set fcp tone to -20 db for 0vu in a +4 balanced environment.
this is also 0 on digibeta over sdi. you might have some 600ohm issues as well.
this is one for system fascist Bob Zelin… /:-|( -
Surely 0 on digibeta is clip (big no no) I’m in the UK and I assume that 0dbVU is -18db(digital) 4ppm.
Full +4db balanced environment, I would assume that I could adjust the output of my card so that the meters in FCP match the meters on the Digibeta Deck. I know that the PPM’s are calibrated because I’ve used them with a Silver for the last 6 months and (despite the idiosyncrasies of the Silver hardware) they were lined up with the decks.
My neck is on the line a bit because I persuaded the head of facilities at the prod co I’m working at that my FCP rig is the money. This is the sort of thing that he would sneer at (he’s just bought a couple more Avids, Express Pros, to go with his Symphony and Media Composers) so I need to get it all looking like a proper OnLine (lets hope Apple has fixed the XML issues with Logic 7.1) Oh yeah, I have to do my own dubs for this series as well…….and shooting………and graphics………and did I mention I was directing too (what happened to real budgets?) -
sorry I meant -20 on fcp is -20 digital on the digibeta which is 0vu analog balanced +4db. post a question for Bob Zelin as he knows his system integration.
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Ta
Bob? Bob? Hello?
Lex
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this is not a detailed enough answer (I am leaving for NAB tomorrow, and have to go to work now), but 0VU varies from manufacturer to manufacturer, and the -14, -18, -20 are all RELATIVE audio levels, and each manufacturer decides on their own setting. All these mean are -14db before clipping, -18db before clipping, and -20db before clipping. All WE care about is WHERE THE HELL IS ZERO, so I can get my equipment to match. Unfortunately, it’s not that easy.
-14 was originally used by AVID and Digidesign for their zero reference. As the years went on, AVID allowed you to go into the Audio Tool, to change where the zero reference was set (so you could make it say -20 for 0VU for example). And yes, 0VU on an AVID is +4dBu (or +4dBm for you Sony and old guys). Sony has ALWAYS used -20db as their zero reference, however, in the beginning, Panasonic was the big DAT machine manufacturer, and the SV3700 DAT has it’s AES input calibrated for -18dB to indicate zero, so you would try to import tapes from a Panasonic DAT, and everything would look screwey – and everyone said the same thing – WHERE THE HELL IS ZERO.
Professional audio equipment that is manufacturered today USUALLY use +4dBu as their zero point, but you will find that just becuase you unpack a brand new Beta 1800 VTR out of the box, does not mean that it’s going to be critically calibrated to +4dBm. I was shocked to recently discover that the # 1 mixer that I recommend (the Behringer UB2442FXPro, which is only $299) has it’s zero mark at 0dBu, and to get a +4db signal out of it, you have to move the faders up two yellow LED’s, where is is actually silk screened on the metal +4.
So whats the answer – EXTERNAL AUDIO METERS. And yes, they usually cost more than your little audio mixers.
bob Zelin
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thanks for your reply, bob
so basically trust my PPMs, ignore FCP meters and (as I’m mastering to Digibeta) stay away from 0. The show is for discovery and they specify no audio above -10dbVU (digital). So at least with my problem (audio coming out hotter than FCP shows) I won’t be doubling up quiet tracks to get more level.
Have fun at NAB – stay away from the roulette tables.
Lex
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not to throw a wrench in things, but we occasionally (and very rarely) have seen a random +3db increase in output from fcp with uncompressed cards. ie fcp set to -20 digital output showing +3db analog throught the card instead of the ususal 0db. this was very rare and showed up on the original digital voodoo cards from years ago and as recently as a year ago with decklink cards. tech support was never able to confirm this, but we were not the only ones. it would mysteriously dissapear with driver updates.it was rare but it would rear it’s ugly head now and again (“oh, no, that +3db thing again!”)
I will say that audio levels from fcp have been remarkably stable and accurate – this over many years, in uncompressed systems, in different facilities, with professionally installed balanced audio environments with many different VTRs (including digibeta, beta sp, 3/4 etc all on the same analog router) with professional metering. where we have seen the biggest problems is the ghost 600 ohm termination promblem with decks like the sony dvw 1800 betasp. they seem to have a different spec than digibetas. mr. coleman from the coleman metering products ( we own his products) Bob Zelin mentioned in his posts tried to explain this 600 ohm termination problem to me – he seemed to make sense, but way above my head. it seems there is no consistency with audio products, especially when relating to digital, and on top of that the UK looks at things differently as well. oh well, our system works!
not much help am I ? sorry -
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Thanks for replys, guys.
Nico
That is exactly what I’m looking for. My control panel hasn’t got any audio settings.
Am I being dim? Latest Drivers installed.
Lex
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unfortunately only a dream. Is only a Picture assembly of me.
BMD should work on so a function! I need it also!
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